U.S. Pat. No. 5,036,122 teaches adhesive compositions for bonding metals to rubbers based generally on polybutadiene latex said polybutadiene desirably having at least one halogen from the group of chlorine, bromine, or iodine. The composition further comprises a poly-C-nitroso compound and a polymaleimide. The adhesive (as explained in column 4, lines 26-39) is always applied over a primer or adhesive primer. The use of a primer implies that the adhesive does not inherently have good adhesion to the bare metal substrate during expected use conditions.
U.S. Pat. No. 5,200,459 teaches a poly(butadiene) latex prepared by emulsion polymerization in the presence of polyvinyl alcohol and a stabilizing solvent. The latex prepared according to this invention supposedly has less problems with coagulation due to the use of polyvinyl alcohol and a stabilizing solvent as a partial or total replacement for conventional surfactants.
Adhesives other than those of U.S. Pat. No. 5,036,122 are usually solvent-based and thus generate volatile organic emissions when used in the workplace.
The purpose of this invention was to create a water-based adhesive and a process using said adhesive capable of bonding metal to rubber formulations that does not require an organic primer or a separate priming step with said primer. Thus, it was desired to make a one package coating that requires only a single application over bare metal or phosphitized metal.